Yep, that was the motivation =). Although i did write my own function to calculate the number of years, so that i would take into account leap years. Surprisingly, not many solutions exist for that...
Going off that. It would be pretty cool if there was an app that showed your average death-date but also connected to multiple platforms to show extensions in your death date. Hey you got your resting heart rate down X, ran Y miles last month and had cholesterol drop Z, you extended your life an estimated ~1.5 years!
It seems to operate off of a unix timestamp and doesn't mind future values, so throw the unix timestamp of your expected death-date in there and watch it count down :)
Have tried similar, and included a widget on my phone's home screen. Moved too slowly to be motivating/demotivating, though could be interesting longer-term.